1. Zinc sulfide   CuO   AgBr   ZnS   MgS   Hint Hint       2. Cupric oxide (Copper [II] oxide)   PbO   CuO   CuCl   NaI   Hint       3. Zinc oxide   ZnO   KBr   KCl   HCl   Hint       4. Ferrous sulfide (Iron [II] sulfide)   FeS   PbO   NaCl   MgO   Hint       5. Sodium iodide   CuCl   KI   ZnO   NaI   Hint       6. Magnesium sulfide   KOH   MgS   HgO   NaOH   Hint       7. Mercuric oxide (Mercury [II] oxide)   HCl   ZnO   MgO   HgO   Hint